The win marked Waterhouse’s 125th success at racing’s highest level, edging her past Lee Freedman into third on the all-time Australian group 1 winners' list behind her legendary father Tommy Smith and Bart Cummings.

It was also Waterhouse’s seventh group 1 of the season.

In a thrilling duel over the latter stages, Cosmic Endeavour ($5) was able to barge through a narrow opening at the 250m-mark and hold off the fast finishing Angel Of Mercy ($26) and Avoid Lightning ($10) in the $500,000 feature.

The margins were a long head by a half head.

Adrian Bott, racing manager for Waterhouse, said Australia’s first lady of racing was a ‘‘phenomenon’’.

Waterhouse is on holidays in England with her husband Robbie but is expected to be back in Sydney next week.

''She (Gai) is an absolutely amazing trainer,’’ Bott said. ‘‘She’s undoubtedly one of the best we’ve seen. It’s been a great thrill for me to work alongside her and gain experience. She’s a phenomenon.’’

Cosmic Endeavour, a three-year-old filly raced by Don and Judy Kelly, has displayed immense toughness over a lengthy campaign throughout the autumn and winter, rising to group 1 level.

‘‘I hope Gai saw that in England. I’m sure she did,’’ Bott said. ‘‘It was a phenomenal win from a very progressive filly.

‘‘She’s a filly that has kept improving with racing.

‘‘She’s a very tough filly who has had a long campaign but has kept improving every start. I’m pretty sure she’ll have a break now and Gai will plot a course for the spring carnival.

‘‘It’s great for Don and Judy, who have been great supporters of the stable. I’m very happy for them.’’

Cosmic Endeavour, a $260,000 yearling, gave notice of her impending climb to fame by winning the group 2 Sapphire Stakes at Randwick in April. However, since coming to Queensland the Northern Meteor filly has thrived.

After winning the Inglis Guineas at Scone, Cosmic Endeavour scored an emphatic win in the group 2 Dane Ripper Stakes at Eagle Farm on June 7.

‘‘It’s been one step at a time with the horse, but Gai has always had a good opinion of her,’’ Bott said.

‘‘I’m sure she’ll take further improvement from today and we can look forward to a good spring.’’

Winning jockey Tommy Berry, who has returned from Hong Kong on two occasions to continue his association with Cosmic Endeavour, was full of praise for the filly and the Waterhouse stable.

The win was the pin-up jockey’s ninth 'major' of the season, with four in Australia, four in Hong Kong and one in Singapore.

‘‘It’s a great pleasure to come back here for Gai and win for all of the team,’’ Berry said.

‘‘This filly has been up for a long time but full credit to her, she’s thrived and kept on improving.’’

Berry admitted he had to ‘‘barge out’’ at a vital stage in the straight to gain clear running.

‘‘Sometimes when you get knocked like that it takes something out of the horse, but to Cosmic Endeavour’s credit, she balanced up and refused to give in right to the line.

‘‘She had to overcome a bump, a good field and I don’t think she was really well served at the weights (55.5kg) against the older mares.’’

The runs of the minor placegetters were outstanding, both horses making up a lot of ground from back in the field to be right in the finish. The Chris Waller-trained Catkins, which was well supported, finished a brave fourth.